“Even though JavaScript is single-threaded, IO in Node.js can happen in parallel due to its async nature. AVA takes advantage of this and runs your tests concurrently, which is especially beneficial for IO heavy tests. In addition, test files are run in parallel as separate processes, giving you even better performance and an isolated environment for each test file... Having tests run concurrently forces you to write atomic tests, meaning tests don't depend on global state or the state of other tests”.

Alex Bolboaca "How to Organize A Code Retreat" - “Developers don’t use abstractions – the usual one is that they use arrays to represent the board in Conway’s Game of Life (hint: if you changed the board to be in 3D, or hexagons, or pentagons, what would happen to the code?)”.